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RRB Group D Number System Questions with Answers & Explanations

20 Number System questions from the Mathematics section of RRB Group D, each with the correct answer and a worked explanation. Try each question first, then tap Show answer to check. When you're ready, take the timed chapter-wise test to see your all-India rank.

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Question 1

What is the square root of 1521?

  1. A39
  2. B36
  3. C40
  4. D41
Show answer
Answer: (A) 39 39 × 39 = 1521.
Question 2

What is the value of 56² − 24²?

  1. A2660
  2. B2560
  3. C2460
  4. D2592
Show answer
Answer: (B) 2560 a² − b² = (a + b)(a − b) = 80 × 32 = 2560.
Question 3

What is the remainder when 65623 is divided by 9?

  1. A6
  2. B4
  3. C5
  4. D3
Show answer
Answer: (B) 4 65623 = 9 × 7291 + 4.
Question 4

What is the HCF of 70 and 98?

  1. A14
  2. B7
  3. C28
  4. D70
Show answer
Answer: (A) 14 70 = 14 × 5 and 98 = 14 × 7, so HCF = 14.
Question 5

What is the unit digit of 17^84?

  1. A1
  2. B8
  3. C0
  4. D4
Show answer
Answer: (A) 1 Unit digits of powers of 7 repeat in a cycle of 4; 84 mod 4 = 0, so the unit digit is 1.
Question 6

What is the sum of the first 92 natural numbers?

  1. A4278
  2. B8464
  3. C4370
  4. D4186
Show answer
Answer: (A) 4278 Sum = n(n + 1)/2 = 92 × 93/2 = 4278.
Question 7

What is the value of 98² − 20²?

  1. A6084
  2. B9204
  3. C9304
  4. D9104
Show answer
Answer: (B) 9204 a² − b² = (a + b)(a − b) = 118 × 78 = 9204.
Question 8

What is the square root of 324?

  1. A17
  2. B18
  3. C15
  4. D20
Show answer
Answer: (B) 18 18 × 18 = 324.
Question 9

What is the HCF of 42 and 56?

  1. A7
  2. B42
  3. C14
  4. D28
Show answer
Answer: (C) 14 42 = 14 × 3 and 56 = 14 × 4, so HCF = 14.
Question 10

What is the sum of the first 71 natural numbers?

  1. A2627
  2. B5041
  3. C2485
  4. D2556
Show answer
Answer: (D) 2556 Sum = n(n + 1)/2 = 71 × 72/2 = 2556.

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Question 11

What is the unit digit of 9^65?

  1. A6
  2. B3
  3. C9
  4. D2
Show answer
Answer: (C) 9 Unit digits of powers of 9 repeat in a cycle of 4; 65 mod 4 = 1, so the unit digit is 9.
Question 12

What is the remainder when 91770 is divided by 11?

  1. A8
  2. B2
  3. C5
  4. D9
Show answer
Answer: (A) 8 91770 = 11 × 8342 + 8.
Question 13

What is the value of 86² − 25²?

  1. A3721
  2. B6871
  3. C6832
  4. D6771
Show answer
Answer: (D) 6771 a² − b² = (a + b)(a − b) = 111 × 61 = 6771.
Question 14

What is the square root of 9025?

  1. A94
  2. B95
  3. C97
  4. D92
Show answer
Answer: (B) 95 95 × 95 = 9025.
Question 15

What is the LCM of 8 and 12?

  1. A28
  2. B24
  3. C48
  4. D12
Show answer
Answer: (B) 24 LCM = HCF × 2 × 3 = 24.
Question 16

What is the sum of the first 45 natural numbers?

  1. A1035
  2. B1080
  3. C990
  4. D2025
Show answer
Answer: (A) 1035 Sum = n(n + 1)/2 = 45 × 46/2 = 1035.
Question 17

What is the unit digit of 13^33?

  1. A5
  2. B9
  3. C1
  4. D3
Show answer
Answer: (D) 3 Unit digits of powers of 3 repeat in a cycle of 4; 33 mod 4 = 1, so the unit digit is 3.
Question 18

What is the remainder when 12002 is divided by 7?

  1. A4
  2. B3
  3. C5
  4. D6
Show answer
Answer: (A) 4 12002 = 7 × 1714 + 4.
Question 19

What is the value of 72² − 49²?

  1. A529
  2. B2783
  3. C2883
  4. D2806
Show answer
Answer: (B) 2783 a² − b² = (a + b)(a − b) = 121 × 23 = 2783.
Question 20

What is the square root of 625?

  1. A25
  2. B27
  3. C22
  4. D24
Show answer
Answer: (A) 25 25 × 25 = 625.

These are RankerClub practice questions written in the RRB Group D pattern. They are not official SSC/IBPS/RRB papers.

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